1. Field of the Invention
The present invention generally relates to a storage system and its management method, and particularly relates to technology of managing the logical volumes in a storage system adopting remote copy.
2. Related Art
In order to prevent the loss of data caused by failure of a storage apparatus, data stored in a certain logical volume of the storage apparatus is usually backed up in a logical volume of a physically separate storage apparatus configured redundantly. As this kind of backup technology, for instance, there is technology known as remote copy (or remote mirroring). The remote copy technology manages data by copying data synchronously or asynchronously between a logical volume in a primary storage apparatus and a logical volume in a backup storage apparatus defined as having a pair relationship therewith. Thereby, even if a failure occurs in the primary storage apparatus, the backup storage apparatus is able to succeed the I/O access requests from applications in the host apparatus.
Further, even when changing the system configuration as a result of the existing storage apparatus being insufficient in terms of capacity or function and it is necessary to replace this with a new storage apparatus, or newly add a separate storage apparatus, data stored in a certain logical volume in the storage apparatus must be migrated to another logical volume.
In the foregoing case, particularly with large-scale computer systems, “nondisruptive operation” of switching the storage apparatus (or its logical volume) without disrupting the execution of applications in the host apparatus is demanded. The host apparatus comprises a mechanism for switching the I/O access path in a state of “nondisruptive operation” of applications.
For instance, Japanese Patent Laid-Open Publication No. 2006-92054 discloses technology for changing the storage apparatus to be I/O accessed by the host apparatus without disrupting applications. Specifically, in a system including an initiator and a target, a first device having a target instructs a second device to create a target having an identifier that is the same as the identifier given to its own target. Subsequently, the initiator uses the same identifier as the one used in the communication path established with the first device to establish a communication path with the target created in the second device. The first device thereafter cuts off the communication path between its own target and the initiator, and the initiator uses the communication path established with the second device to continue the communication with the target having the same identifier.
In a storage system using the remote copy technology, when a pair relationship is defined between logical volumes in a storage apparatus, the same identifier is given to the logical volumes. Thus, the host apparatus is able to switch from a certain logical volume of the I/O access destination to another logical volume without disrupting the execution of applications with the switching function of the I/O access path.
Today, when the migration (copy) of data between logical volumes in a pair relationship is complete and such pair relationship is thereafter cancelled due to changes in the system configuration or the like, the logical volume of the migration source must continue to use the identifier of the logical volume of the migration source under conditions of nondisruptive operation of applications. Further, if a logical volume of the migration source no longer having a pair relationship uses the logical volume of the migration source, there will be contradictions in the system configuration due to conflict of identifiers, and the host apparatus will not be able to properly recognize the logical volume in the storage system.